Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$38.50	10.562%	$42.5664	$42.57	$42.55	$42.60
Purchase #2	$123.39	10.350%	$136.1609	$136.16	$136.15	$136.20
Purchase #3	$182.39	13.443%	$206.9087	$206.91	$206.90	$206.90
Purchase #4	$237.42	7.325%	$254.811	$254.81	$254.80	$254.80
Purchase #5	$249.55	5.130%	$262.3519	$262.35	$262.35	$262.40
Purchase #6	$38.89	6.338%	$41.3548	$41.35	$41.35	$41.40
Purchase #7	$147.42	6.303%	$156.7119	$156.71	$156.70	$156.70
7 purchase totals =	$1,017.56		$1,100.8656	$1,100.86	$1,100.80	$1,101.00